The present invention relates to fittings used to connect miniature fluid conduits, and especially fittings used to connect miniature fluid conduits utilized in liquid chromatography.
Numerous types of equipment used for the analysis or purification of chemical compounds utilize miniature fluid conduits, such as metallic tubing, within which liquid samples pass through the system. For example, liquid chromatography is a technique in which a column is packed with a packing material, an analyte is introduced into one end of the column, and a carrier fluid is then run through the column. The length of time that the analyte is retained within the column can enable analysis and identification of the analyte. A popular form of liquid chromatography is High Performance Liquid Chromatography (HPLC) in which the sample is pumped through the column under an elevated pressure, typically at 300 to 6,000 psi.
Liquid chromatography systems, such as HPLC systems, typically include several components, for example; a pump; an injection valve for injecting the analyte; a precolumn filter to remove particulate matter in the analyte solution that might clog the column; a guard column to retain irreversibly adsorbed chemical material; the HPLC column itself; and a detector that analyzes the carrier fluid as it leaves the column. These various components may typically be connected by a miniature fluid conduit, such as metallic or polymeric tubing, usually having an internal diameter of 0.005 to 0.040 inch. All of these various components and lengths of tubing are typically interconnected by threaded fittings. Often, a first internally threaded fitting seals to a first component with a ferrule or similar sealing device. The first fitting is threadedly connected through multiple turns by hand or by use of a wrench or wrenches to a second fitting having a corresponding external fitting, which is in turn sealed to a second component by a ferrule or other seal. Disconnection of these fittings for component replacement, maintenance or reconfiguration again requires the use of a wrench or wrenches to unthread the fittings. Most thread connections are 10-32, xc2xc-28 or 6 mmxc3x971. If a hand-tightened threaded fitting is used, it may not stand up to the extreme pressures of HPLC.
The present invention provides a quick connect fitting assembly for coupling first and second analytical fluid conduits. The assembly includes a first fitting defining a central passage for receiving the first fluid conduit therein, the first fitting defining at least one first radial engaging surface, and a second fitting defining a central passage for receiving the second fluid conduit therein. The assembly further includes an annular nut rotatably mounted on the second fitting, wherein the nut defines at least one second radial engaging surface, wherein the nut is selectively rotatable less than 360xc2x0 relative to the first fitting to engage the first and second engaging surfaces to create a secure seal between the first and second fittings for fluid flow communication between the first and second fluid conduits.
A preferred embodiment of the present invention provides a quarter turn quick connect fitting assembly, including a first fitting having radially projecting connecting protrusions and a second fitting having grooves which receive the connecting elements, which is operable by twisting one of the components by less than a full turn, preferably by a xc2xc turn. Both the first and second fittings define a central passage which may be configured to slidably receive a hollow tube, or which may be internally threaded to threadedly receive an externally threaded mating fitting. The first and second fittings are selectively connected by sliding the connecting elements of the first fitting into the grooves of the second fitting and rotating the quarter turn nut through approximately 90xc2x0 with respect to the first fitting. The connecting elements are thereby securely seated within angled areas at the inner ends of the grooves.
In a first preferred embodiment of the quarter turn quick connect fitting, the first fitting includes a body having a proximal end and a distal end. Two pins radially project from the distal end of the first fitting. The body of the first fitting defines a central passage extending from the proximal end of the first fitting to a centrally located recess on the distal end of the first fitting. The central passage can be configured to slidably receive a hollow tube set, or to threadedly receive an externally-threaded mating fitting. The second fitting includes a body having a proximal end and a distal end. A central passage extends from the proximal end of the first fitting to a centrallylocated recess on the distal end of the first fitting. The central passage can be configured to slidably receive a hollow tube set, or to threadably receive an externally-threaded mating fitting. The second fitting is mounted within a rotatable nut, and is biased therein by at least one spring washer. The rotatable nut has a proximal end and a distal end, and includes two spiral grooves which open onto the distal end of the nut. The two spiral grooves receive the two dowel pins of the first fitting, thereby coupling the first fitting to the quarter turn nut, as set forth above. A compressible sealing element, having a body defining a central passage, is located between the first and second fittings and forms a seal when the first and second fittings are locked together. The central passages of the first fitting, the sealing element and the second fitting thus form a continuous, sealed passage within which there is no deadspace to reduce or interrupt fluid flow therein, or cause band broadening of the analyte sample.
A second preferred embodiment of the present invention is similar to the first preferred embodiment, except that the central passage of the first fitting is beveled at the proximal end and is configured to slidably receive an HPLC column end fitting. The first fitting is externally threaded and is retained on the column end by means of an internally threaded nut mounted coaxially around the HPLC column end fitting and which is screwably attached to the externally threaded surface of the first fitting. A seal is formed between the beveled surface of the central passage of the first fitting and a ferrule mounted coaxially around the HPLC column end fitting.
A third preferred embodiment of the present invention is similar to the first preferred embodiment, except that the central passage of the first fitting is internally threaded to receive the externally threaded end of a BPLC column.
In a fourth preferred embodiment of the present invention, the quarter turn quick connect fitting includes a first fitting having a central passage internally threaded to receive a HPLC column end fitting, as described for the third preferred embodiment, and a second fitting located within a quarter turn nut. The fourth preferred embodiment of the present invention further includes an adapter having a body defining a central passage. The adapter body has a proximal end and a distal end, the proximal end having two grooves and the distal end having two radially projecting dowel pins. The central passage of the adapter is configured to receive a guard column. The first fitting is connected to the adapter by rotatably inserting the dowel pins of the first fitting into the grooves of the proximal end of the adapter. The second fitting is connected to the adapter by rotatably inserting the dowel pins of the distal end of the adapter into the grooves of the distal end of the quarter turn nut.
In a fifth preferred embodiment, the quarter turn quick connect fitting includes a first fitting, a second fitting located within a quarter turn nut, and a frit composed of a sintered material that filters the fluid passing therethrough. The frit is housed within a frit ring composed of a deformable material that forms a seal between the first and second fitting within the quarter turn quick connect fitting.
Additionally, the second fitting in any of the foregoing preferred embodiments can include a slot extending from the proximal end to the distal end of the second fitting, and completely penetrating one side of the second fitting body. The slot within the second fitting body permits the hollow tube set to be readily disconnected from the second fitting by withdrawing the second fitting from the quarter turn nut cavity and sliding the hollow tube set laterally through the groove in the second fitting body. When the embodiment of the second fitting including a slot is utilized, the second fitting is not fixedly retained within the quarter turn nut. Instead, a retaining ring within the quarter turn nut cavity retains the spring washers. The retaining ring is seated within an annular groove disposed around the circumference of the quarter turn nut cavity. The embodiment of the quarter turn nut having the annular groove can be used with any of the foregoing embodiments of the quarter turn quick connect fitting. Rather than slotting the second fitting, the first fitting can be slotted.
Thus, the present invention provides a quarter turn quick connect fitting for rapidly and easily connecting miniature fluid conduits without creating any deadspace therebetween. Connection is made by a single hand motion, preferably by rotating the fittings relative to each other through a single hand motion without need for changing grip, still more preferably by rotating through no more than 360 degrees, and most preferably by rotating through only a xc2xc turn. A quick connection is thus provided, as compared to the time consuming connection of a conventional, fully threaded connection. During mating of the fittings and after mating, the tubes or other components are axially retained by the first and second fittings acting on positive stops defined by the tubes or associated hardware. The quarter turn quick connect fitting can include one or more frits, screens, or additional stationary phase packing material, such as C18, Silica, etc., for filtering, conditioning or retaining analyte from the fluid passing therethrough. Further, the seal formed within the quick connect fitting will hold when fluid is pumped at high pressure through the assembled quick connect fitting.
The present invention thus provides for the quick and easy connection and disconnection of miniature fluid conduits and fittings that join the components of a liquid chromatography system, or other chemical analytical equipment, so that, for example, the system can be rapidly reconfigured to perform a different type of analysis. The operation of the quick connect fittings of the present invention require only the use of normal manual strength and dexterity, and do not require the use of special tools. Connection and disconnection is provided by a simple xc2xc turn, with the xc2xc turn serving as a retainer member for the first and second fittings. The quick connect fittings of the present invention are able to hold a seal under the relatively high pressures often utilized in liquid chemical analytical systems, such as an HPLC system. Additionally, the quick connect fittings of the present invention do not create any dead volume, i.e., space in which the flow of the analyte would be reduced or interrupted, which would permit the flowing analyte to stagnate and its partially or completely separated components to mix.